Battery separator

ABSTRACT

A battery separator is provided that has a plurality of protrusions extending above the main surface thereof. The protrusions are arranged in an entirely new pattern which permits a minimum total area of the separator to be covered with protrusions and yet assures good contact with all areas of a battery&#39;s grid. This is done by arranging the protrusions in alternating rows in a manner blocking any openings between protrusions with which an element of the battery&#39;s grid could be registered. 
     Another aspect includes a compressible battery separator having compressible embossments.

BACKGROUND OF THE INVENTION

This invention relates to battery separators and the like and moreespecially to those having protruding elements extending above the planeof the main surface thereof.

Battery separators have in the past had main surfaces with membersprojecting thereabove in various patterns as illustrated by U.S. Pat.Nos. 2,694,744; 2,677,008; 2,172,382 and 2,198,845. The separators ofthe prior art have various deficiencies such as having the protrusionsso aligned that while the protrusions would engage the paste of thebattery plate and thereby provide the additional separator spacing theywould not assure contact with substantially all of the grid members.This is illustrated in U.S. Pat. No. 2,694,744 by way of example. Inmany battery grids the horizontal and vertical grid members are notequally heavy. In these instances, the dominant or heavier grid wire ormember is usually the vertical one. In other prior art separators, theprotrusions have been so arranged as to exclude the settling ofmaterials in the battery. Material shed from the battery plates andother materials which might accumulate in the battery should be allowedto fall down to the bottom of the battery. This would not occur with theseparator shown for example in U.S. Pat. No. 2,198,845.

A discussion of various grid designs as well as other backgroundinformation may be found at page 28 and elsewhere in the book, StorageBatteries, by George Wood Vinal, fourth edition, John Wiley & Sons,Inc., New York, copyrighted 1955.

It is an object of the present invention to provide a superior batteryseparator.

It is a further object of the present invention to provide such asuperior battery separator having reduced mass with maximum contact ofthe grid portions of the battery plates by thickened areas of theseparator.

SUMMARY OF THE INVENTION

By an aspect of the invention a battery separator is provided that hasan interrupted pattern of distinct portions. The separator is operablewith a battery plate having a series of parallel spaced apart linearbattery members extending in a first plane. These battery members wouldcommonly be grid members of a battery plate. The separator includes agroup of distinct separator portions arranged in a plane parallel to thefirst plane and in rows that extend diagonally with respect to thespaced apart linear battery members, with distinct portions in some rowsoffset with respect to the distinct portions in other rows so that whenthe separator is in operable relation with the battery members, a linearbattery member cannot be aligned to miss all of the distinct portions.The distinct portions are so shaped that material shed from the plateand other sediment in the battery will not pile up on the distinctportions but will tend to slide off and fall on down in the battery.

In other special aspects the separator is in the form of a rectangularsheet having two outwardly facing opposite faces that have basicallyplanar main surfaces with the rows of distinct separator portionsextending across at least one of these faces at an angle of 30°-60° toeach of the edges of the rectangular sheet. The distinct separatorportions are preferably circular in shape with a diameter of about 1/8inch, a height above the main surface of 15-62 mils and spaced about3/16 inch apart in the rows with the separator having a total thicknessof 18-92 mils.

In other aspects, the broken portions of a battery separator make atleast one continuous coverage separator portion that diagonally crossesat least one vertical grid axis when the separator member is in operablerelation with the battery grid. The broken portions are spread apart onaxes parallel to the grid member they cross diagonally. In a preferredform, the distinct portions contact at least two thirds of the verticaland the horizontal grid elements or members at least twice.

In yet another aspect, the battery separator is compressible.

DESCRIPTION OF THE DRAWINGS

FIG. 1 A top plan view of one face of the preferred separator of thisinvention.

FIG. 2 An enlarged edge view of one form of the separator of FIG. 1.

FIG. 2A An enlarged edge view of another form of the separator of FIG.1.

FIG. 3 An enlarged edge view of another form of the separator of FIG. 1.

FIG. 4 A diagramatic view of the battery separator of FIG. 1 with abattery grid applied thereto in phantom line to show their operablerelation.

FIG. 5 A variant battery separator of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1 of the drawings, a battery separator 10 isshown. The battery separator 10 has a top edge 11, a bottom edge 12 anda first and a second side edge 13 and 14 respectively. The side edgesextend at right angles to the top and bottom edges. The edges define theouter bounds of a rectangular sheet which is shown in actual scale inFIG. 1. The sheet is 53/4 inches wide and 51/4 inches high.

The separator 10 has two outwardly facing opposite faces 15 and 16 (FIG.2) that have basically planar main surfaces. At least six rows ofprojections 17 are formed on and extend across the face 15 of the sheet10 at an angle of 45°. In the embodiment shown there are seven rows ofprojections. The preferred angle at which the projections extend acrossthe sheet is 30°-60° to each of the edges. The projections 17 are spacedabout 3/16 inch apart in the rows and are substantially circular inshape with a diameter of about 1/8 inch and a height above the mainsurface of about 1/16 inch. The preferred height above the surface is15-62 mils with the optimal projection, according to certain aspects,having a diameter of about 1/8inch taken from the opposite planar mainsurface 16. The thickness through the main body of the separator betweenthe main surfaces 15 and 16 is 3-30 mils providing a total separatorthickness of 18-92 mils in the preferred form. The distance between therows is preferably about 15/16 inch.

It is of importance to note that the projections in one row are offsetrespecting the projections in an adjacent row such that no open pathsexist across the face of the battery separator parallel to any edge ofthe separator across two adjacent rows. In other words, any straightline drawn across the separator parallel to any edge of the separatorwill intersect one of the projections 17 if the line extends across twoadjacent rows of projections. If this line coincides with the routefollowed by a battery grid element, then it would clearly be engaged byone of the projections and held away from the main surface of theseparator.

A feature of the invention is found in the operating relationshipbetween the battery separator and the battery grid in the sense that thetwo in combination form the final operating combination. As is known,battery grids are commonly pasted with an active material and thesepasted members are called plates. The battery grid has a plurality ofelements 18 extending along parallel axes as shown in FIG. 4 in phantomline. An additional plurality of elements 19 extends along secondparallel axes crossing the first plurality of elements and forming across grid therewith. These two series of parallel elements in the mostcommon type of automotive battery cross at right angles with a spacingof 1/2 inch. The two series of elements or spaced apart battery membersare usually basically linear and arranged in a common plane. However,other non-linear elements are known and so long as they have acontinuing aspect in a general direction, the rules of this inventionapply. This is true even when the grid is made up of a plurality ofcurved parts. In fact, the grid is normally cast as a unitary part andthus the linear elements are actually parts of cross elements.

The battery separator is operationally installed in normal positionadjacent to the pasted battery grid with the face of the separator withthe projections formed thereon positioned against the pasted batterygrid. The rows of projections extend diagonally across the grid elementsat an angle of 30°-60° with the grid elements necessarily being alignedto fall on some of the projections when the separator and battery gridare shifted relative to one another so long as the diagonal relationshipof the grid elements and the rows of projections remain within the angleof 30°-60°.

Thus, at least two groups of projections or broken separator portionsare arranged in a pattern in an interconnected unit and theseprojections make at least one continuous coverage separator portion thatdiagonally crosses at least two of the linear battery elements when theseparator member is in operable relation with the elements. Bycontinuous coverage separator portion is meant a separator element orportion made up of pieces that form a continuous obstruction or wallwhen viewed from the direction of approach of the battery elements asindicated by the arrows 21 and 22 in FIG. 4. The projections also make asecond continuous coverage separator portion that diagonally crosses atleast two of the linear second battery elements extending on the secondgrid axes. In fact, the projections of the seven rows shown in FIG. 4provide continuous coverage separator portions that diagonally crosssubstantially every one of the first and the second parallel grid axes.The preferred form would require that they diagonally cross at least twothirds of the first and of the second grid axes and contact at least twothirds of these grid elements at least twice. It may be seen that allbut two of the vertical grid elements 18 in FIG. 4 are engaged by atleast two projections 17 and that every one of the horizontal gridelements 18 is engaged by at least two projections 17.

Looking again at FIG. 2, it may be seen that the thickness and the massof the sheet 10 is greater at the projections 17 than at theintermediate region 23 which makes up the greater area of the sheet. Theeffect of this increased thickness is to block off the area. The passageof ions may be said to effectively be limited to the areas of leastresistance, i.e., the thinner intermediate areas 23. Thus, the greaterthe combined area of the projections is the greater the electricalresistance and the lower the final battery electrical capacity will be.

Thus, the spacing apart of the projections 17 is important, as well astheir shape or size. It is desirable to block off the least areapossible with the thickened areas or regions 17. The sheet 10 is cutfrom a long roll that is about 15 inches wide manufactured by acontinuous process the preferred form of which is described in copendingapplication Ser. No. 225,205 filed Feb. 10, 1972 and now U.S. Pat. No.3,798,294. A 51/4 by 53/4 sheet cut from the roll stock will necessarilycontain a minimum of six rows of projections 17 which gives thenecessary minimum amount of separation contact or support to provide thenecessary spacing between the main surface 23 of the separator sheet 10and the battery plate. As shown in FIG. 1, the random cutting of thesheet may produce up to seven rows of projections. The important featureis that substantially two complete continuous coverage separatorportions cross every one of the battery grid elements. In a cross gridthis means two diagonal continuous coverage separator portions in eachdirection or across both sets or series of grid elements. It can be seenthat the same projections may be considered once with respect to thecontinuous coverage separator portion for each series of grid elementsif properly positioned. If this is done, then two hits on every elementare assured which gives adequate spacing support. As shown in FIG. 4,this was achieved in the case of the horizontal grid elements 19, butwas not quite achieved in the case of the vertical grid elements 18.Thus, it may be surmised that if the rows of projections, in the exampleillustrated in FIGS. 1 and 4 were combined, each row with one adjacentrow, two complete continuous coverage separator portions would be formedacross the horizontal grid elements 19 but slightly under two completecontinuous coverage separator portions would be formed across thevertical grid elements 18.

If the projections 17 are physically superimposed, they do not make acontinuous diagonal line. The spacing between the projections is 3/16 ofan inch in a row while the projections themselves have a diameter ofonly 2/16 of an inch. Thus, their blocking or continuous coverageseparator portion value is greater than their actual physical diagonalcoverage if combined. This enables the battery separator in FIGS. 1 and4 to have no more than and generally less than the resistance that wouldbe created by only two continuous ribs across the sheet. Preferably, theraised portions or projections 17 constitute or cover less area than thearea of the face that they do not cover. In other words the projections17 preferably cover less than 50% of the surface area of the separatorface 15 and usually more preferably less than 25% and most preferablyless than 20%.

There is another way of describing the structural relationship betweenthe projections in the separator sheet and the first and second parallelaxes of the grid elements or members. FIG. 4 reveals that in forming acontinuous coverage separator portion applicable to each series of gridelements the projections may be described as being spread apart on thefirst parallel axes and on the second parallel axes to form the rows andbecause they form a continuous coverage separator portion, theynecessarily contact the grid elements on the axes of which the portionsare spread apart.

A variation of the battery separator cross section in FIG. 2 is shown inFIG. 2A. In this variation the tops of the projections 17a areflattened, preferably by secondary calendering as shown in copendingapplication Ser. No. 225,205 which is owned by the same assignee as thepresent invention. This not only assures a uniform projection height,but also aids in stablizing the sheet against being urged to move by itsengagement with the grid members which would tend to try to slide downthe sloping surfaces of the rounded projections 17 of FIG. 2. Theflattened projections 17a may be seen to extend above the intermediateregions 23a.

Another variation of the battery separator cross section of FIG. 2 isshown in FIG. 3. In this cross sectional configuration, the mass of allregions of the sheet 25 are the same. In other respects, the sheet isthe same as separator 10. The preferred sheet 25 of FIG. 3 is alsopreferably made, as taught in U.S. patent application Ser. No. 225,205,from the plastic material of U.S. Pat. No. 3,351,495. The thickness ormass of the separator 25 is maintained constant by providingindentations 26 that extend inwardly into the face 27 of the batteryseparator exactly opposite the projections 28 in the face 29 so that asmay be seen the thickness of the battery separator between theprojections and at the projections is maintained constant.

This battery separator is compressible when made from the preferredresilient material of U.S. Pat. No. 3,351,495. Especially goodcompression qualities are present when the preferred sheet thickness of3-30 mils is present. The compressible battery separator sheet's twoopposite main basically planar faces 27 and 29 are embossed. Theembossments or projections 28 formed in the sheet are discontinuousacross said sheet in the same manner as projection 17. They extend outfrom at least one of the main planar faces and are depressed into theopposite main planar face and compressible toward the main planar facethey extend out from. The sheet's resiliency constantly forces theembossments back toward their non compressed positions when theembossments are compressed. The sheet can be embossed so that adjacentareas of the sheet are formed into projections that extend from oppositesides of the sheet with corresponding opposite depressions.

As shown in FIG. 3, the embossment 28 is a true spherical portion. Thishas been found to give the best stress characteristics undercompression. Other arcuate tent like structures are also satisfactory.However, long ribs and sharp or flat sided projections tend to givestress cracking problems and the like and while in a few specialinstances they may be operable, they are generally not preferred.

Each of the projections in sheet 10 and sheet 25 is preferably shaped sothat material shed from the plates and other sediment in the batterywill not pile up significantly thereon but will tend to slide off andfall on down in the battery. Thus, the individual separator portions orprojections have a substantial upwardly disposed slope. In the preferredform, the arcuate upwardly disposed surfaces of the round projections 17and 28 have this characteristic. Of course, many other shapes could beutilized such as a roof top type arrangement having sloping surfaceswhich would allow sediment to slide downwardly and off of the edgesthereof and other curved surfaces such as oval shaped members.

Turning our attention to the variant form of the invention of thisapplication shown in FIG. 5, it may be seen that in FIG. 5 more than twogroups of broken portions or projections are arranged in a pattern in aninterconnected unit or sheet 30. In this instance three rows of somewhatoval shaped projecting members 31 are arranged to diagonally cross thegrid elements, preferably at the preferred angle of 30°-60° aspreviously set forth. This assures that the grid elements will bealigned to fall on some of the projections if the separator and batterygrid shift relative to one another so long as the diagonal relationshipof the grid elements and the rows of projections remain within theintended angle. It may be seen for example, that one cannot draw a lineacross the separator 30 from the top side 32 to the bottom side 33 at aright angle to the top 32 without crossing one of the projecting members31.

The projecting members 31 are curved at their upper ends 34. Thus,sediment falling down along the face 35 of the separator 30 will not beretained on the upper surfaces of the projecting members 31.

Certain aspects of the separator of the present invention may bedescribed mathematically. The raised means or projections 17 will belocated on the separator 10 with reference to an arbitrary scalingsystem. The vertical scale will be assigned K evenly spaced incrementsand the horizontal scale will be assigned J evenly spaced increments. krepresents any location on the vertical scale and j will represent anylocation on the horizontal scale. Now the location of a projection, D,can be established by the notation D (j,k) where k and j take onappropriate K and J scale values.

Now if it is desired to block the passage across the face 15 of theseparator 10, a continuous vertically and horizontally blocking seriesof D's must be arranged across the separator. In carrying out thisdesire, the rule may be postulated that every j unit and every k unitmust always be used. Then given an initial pattern of D's that satisfiesthe rule, variations of pattern can be made by moving the projectionsabout on the separator in definable ways that will not disrupt thecompleteness of the blocking value. A mathematical description of themoving rules that have just been described may be illustrated asfollows.

    D.sub.1 (j.sub.1,k.sub.1 ) → D.sub.1 (j.sub.1,k.sub.2)

    D.sub.2 (j.sub.2 ,k.sub.2) → D.sub.2 (j.sub.2,k.sub.1)

    D.sub.1 (j.sub.1,k.sub.1) → D.sub.1 (j.sub.2,k.sub.1)

    D.sub.2 (j.sub.2,k.sub.2) → D.sub.2 (j.sub.1,k.sub.2)

These formulas describe the pair wise movement of projections such thatif one projection is arbitrarily moved to a new location a secondprojection can be identified and appropriately moved to a new locationto establish a new pattern with the same blocking value.

This system can be easily visualized in application to FIG. 1 where Kcould be assigned to the vertical edge 13 of the separator 10 and Jcould be assigned to the lower edge 12. Then the projections 17 could bemoved about on the face 15 of the separator by application of the systemwithout sacrificing the completeness of the blocking value.

Another valuable rule to apply is to be sure that a substantially equalnumber of D's are present in the end product in each quadrant of theface. It may be appreciated that if the raised means D are notdistributed substantially evenly on the face of the separator, one faceof the separator might have its basic surface level engaged directlyagainst the material the raised means are intended to space the basicsurface level from. Thus, the raised means should be distributed on theface substantially evenly if the face is bisected vertically andhorizontally into four equal parts. The distinct separator portions insome rows are offset with respect to the distinct separator portions inother rows so that when the separator and the member having the grid arein normal operable relation the first series of grid elements and thesecond series of grid elements will necessarily be aligned to fall onsome of the distinct separator portions in any position in which theseparator may be shifted while maintaining the diagonal relationship ofthe rows of distinct separator portions and the series of grid elements.Thus, a separator is provided that when matched in normal operableposition with a battery grid will assure proper spacing in the batteryirrespective of the positioning of the separator and the battery gridwith respect to one another, so long as the angle is maintained. Inother words, in cutting the manufactured separator sheet which would bemuch larger than the individual separator in normal circumstance, it isnot necessary to make sure that the sheet is cut in exactly the sameposition with regard to individual separator portions as would be thecase with portions that would have to be positioned specifically tocontact individual grid wires or elements. Furthermore, the sheet may becut so that its machine direction forms either the vertical or thehorizontal direction when the separator is used.

While for simplicity and clarity, the invention of this application hasbeen described in general with respect to discrete sheets cut to conformto use with a single face of a battery plate, the invention isanticipated to have even greater value for application in longerrectangular sheet form for "wrapping" a series of battery plates. Bywrapping, it is to be understood that a specific length of separatormaterial is preferably formed into an S wrap around juxtapositionedbattery plates for use in a single battery cell. A single long piece ofseparator material can thus have face 15 at one end of sheet 10 (FIG. 2)placed against the first outer positive plate. The sheet is then bentaround the edge of the positive plate and face 15 is engaged against theback of the positive plate. This places the face 16 of the sheet 10against the adjacent negative plate. The sheet 10 is then bent aroundthe edge of the negative plate and the face 16 is engaged against theback or opposite side of the negative plate. This engages the face 15against the adjacent positive plate. The sheet is then bent around theedge of the positive plate and so on until the sheet is woven back andforth through the plate assembly for a battery cell. This in effectprovides the separator characteristics of the independent discreteseparator sheets to each battery plate face.

The improved battery separator of this invention has a first face with afirst basic surface level having a plurality of independent meansextending thereabove. The independent means is discontinuous across theface both vertically and horizontally and yet no open path exists acrossthe face either vertically or horizontally. To facilitate the passage ofsediment around the independent projecting means, they have continuouslyconvex outer side surfaces and to aid uniformity of thickness in theseparator sheet, the outer tips of the projections are flat.

The separator material of this application can also be formed intoenvelopes that may be slipped over the individual positive plates. Theouter inside faces of the envelope would be composed of face 15 whilethe outside face would be composed of face 16. Of course, both faces mayon occasion have the structure illustrated only on face 15 in thedrawings of this application. The face 16 could also have otherstructures such as slight ribbing.

By another feature of the invention of this application, a superiorcompressible battery separator is provided that allows the batteryplates and separators for a cell to be assembled and then mechanicallycompressed and inserted in a cell compartment achieving a secure fitwithout the use of shims.

It will be obvious to those skilled in the art that various changes andmodifications may be made in the invention without departing from itstrue spirit and scope. It is, therefore, aimed in the appended claims tocover all such equivalent variations as fall within the true spirit andscope of the invention.

We claim:
 1. In a battery, having a battery plate and a battery separator, said separator having a top edge, a bottom edge and a first and a second side edge defining the outer bounds of a rectangular sheet having a face with a plurality of projections thereon spacing said face from said battery plate the improvement comprising arranging said plurality of projections on said separator so as to be discontinuous across said face both vertically and horizontally and positioned so that no open path exists across said face vertically or horizontally, said projections covering less than 25% of the surface area of said face.
 2. In the battery of claim 1, said battery separator's projections spaced apart a greater distance than their greatest dimensions.
 3. In the battery of claim 2, said battery separator's projections arranged in at least six rows formed extending across said face at an angle of 30°-60° to each of said edges, the projections in each row having open paths therebetween across the face of said separator parallel to any edge of the separator and the projections in adjacent rows offset to thereby provide that no open path exists across the face of said separator parallel to any edge of the separator.
 4. In the battery of claim 3 wherein said battery separator's projections are substantially uniform in dimension, substantially circular in shape, spaced apart in the rows about 3/16 inch, have a diameter of about 1/8 inch and a height above the main surface of 15-62 mils with the separator having a total thickness of 18-92 mils, said projections covering less than 20% of the surface area of said one face.
 5. In the battery of claim 3 wherein said battery separator's projections have flat outer tips, continuously convex outer side surfaces and said separator has a second face facing outwardly opposite said first face, the first said face and said second face having basically planar main surfaces with said second face having no projections thereon.
 6. In the battery of claim 3 wherein each of said battery separator's projections is shaped so that material shed from the plates of said battery and other sediment in the battery will not pile up significantly thereon but will tend to slide off and fall on down in the battery.
 7. The battery of claim 2 wherein said battery has pasted battery plates with a plurality of grid elements crossing one another at right angles and arranged in a first plane, said battery separator being positioned adjacent to said grid elements with at least a portion of its face having said projections positioned against said grid elements; said projections arranged in rows extending diagonally across said grid elements at an angle of 30°-60° with said grid elements each being aligned to fall on at least one of said projections when the separator and grid elements are shifted relative to one another so long as the diagonal relationship of the grid elements and the rows of projections remains within an angle of 30°-60° and wherein said grid elements crossing one another at right angles extend along first parallel axes and second parallel axes respectively and said projections are spread apart on the first parallel axes and the second parallel axes to form said rows and to form continuous coverage separator portions that contact said grid elements on the axes of which its portions are spread apart.
 8. In the battery of claim 7 wherein said battery separator's projections contact at least two thirds of said grid elements at least twice.
 9. In a battery with pasted battery plates having a plurality of grid elements crossing one another at right angles and extending along first parallel axes and second parallel axes respectively and arranged in a first plane, and an improved battery separator, said battery separator being a discrete rectangular sheet having a top edge, a bottom edge and first and second side edges extending at right angles to said bottom edge; said sheet having two outwardly facing opposite faces that have basically planar main surfaces; the improvement comprising at least one of said faces having at least six rows of projections formed on and extending thereacross at an angle of 30°-60° to each of said edges; said projections being of substantially uniform dimensions, substantially circular in shape, spaced apart a greater distance than their diameter and covering less than 25% of said face; the projections in one row offset respecting the projections in an adjacent row such that no open path exists across the face of said battery separator parallel to any edge of the separator across two adjacent rows and said projections spread apart on said first parallel axes and said second parallel axes in said rows and forming continuous coverage separator portions; and said battery separator being positioned adjacent to said pasted battery plate with said face with said projections formed thereon positioned against said battery grid with said rows extending diagonally across the grid elements at an angle of 30°-60° with said projections contacting all of the grid elements at least once and two thirds of said grid elements at least twice when the separator and battery grid are shifted relative to one another so long as the diagonal relationship of the grid elements and the rows of projections remains within an angle of 30°-60°; the shape of said projections causing material shed from the plates and other sediment in the battery to tend to slide off and fall on down in the battery and not pile up significantly on said projections. 